The invention relates to a communication system having a plurality of communication devices, a plurality of communication terminals and a communication network connecting the communication terminals to the communication devices, in which case a first address for a connection to a home communication device assigned to a specific communication terminal and a second address for a connection to an alternate communication device is stored in the communication terminals in each case.
On the basis of an increasing global alignment of enterprises, the application of telecommunication services for transmitting voice and data is continuously increasing. This results in the fact that the costs incurred by these telecommunication services are continuously rising and are becoming a considerable cost factor for enterprises that are looking for opportunities to reduce these costs. Local and global computer networks such as the ‘intranet’ or the ‘Internet’ offer the possibility of transmitting data cost-effectively and world-wide. In this case, realtime critical data, for example, voice and video data is also increasingly being transmitted via such local and global package-oriented networks.
On the ‘intranet’ or the ‘Internet’, one or more centralized devices referred to in the literature as servers, communicate in each case with one another or with remote decentralized devices—referred to as clients in the literature. Examples of decentralized devices are stationary or portable computers, Internet Protocol-enabled telephones, etc. Communication takes place by using so-called Internet protocols, especially the Transmission Control Protocol/Internet Protocol. In this case, software that can understand and evaluate the Transmission Control Protocol/Internet Protocol—often referred to as ‘socket’ or ‘TCP/IP stack’ in the literature—is implemented in each case in the respective centralized and decentralized devices.
In order to transmit voice data starting from or for an Internet Protocol-enabled terminal, special centralized devices are usually provided in a computer network that are referred to as gatekeeper in the literature. In this case, one gatekeeper is usually permanently assigned to each Internet Protocol-enabled terminal that is designated as a home gatekeeper below. Therefore, a gatekeeper has the function of a centralized control element that controls a connection setup to or from the Internet Protocol-enabled terminal via the computer network. In this case, terminal-specific data—referred to as a terminal profile below—is stored in the gatekeeper by means of the control of the connection setup or the setup connection. The terminal-specific data then includes, amongst others, a call number assigned to the terminal, a subscriber assigned to the terminal or authorizations assigned to one of the terminals, keyboard layouts stored for the terminals, etc.
In addition to storing the terminal profile in the home gatekeeper, a further terminal profile is stored for each terminal in an alternate gatekeeper so that for cases in which the home gatekeeper or a part of the computer network assigned to the home gatekeeper fails or is interrupted, the connection setup or the connection can be routed through the alternate gatekeeper.
FIG. 1 shows the structure of a communication system KS developed according to the related art with several gatekeepers G-A, G-B, G-C, several communication terminals KE1, KE2, KE3 and a communication network IP-N connected to the communication terminals KE1, KE2, KE3 with the gatekeepers G-A, G-B, G-C. In this embodiment the data transmission via the communication network IP-N is based on the Internet Protocol in which case the communication terminals are KE1, KE2, KE2 Internet Protocol-enabled terminals. Alternately, the communication network IP-N can also be developed as a mobile radio network and the communication terminals KE1, KE2, KE3 as mobile radio terminals.
A first gatekeeper G-A is connected to the communication network IP-N via a network segment N-A, a second gatekeeper G-B via a network segment N-B and a third gatekeeper G-C via a network segment N-C. The first gatekeeper G-A is assigned as home gatekeeper to a first communication terminal KE1 with the call number 4711. Therefore, a terminal profile P4711 assigned to the first communication terminal KE1 is stored in the first gatekeeper G-A. The second gatekeeper G-B is assigned as home gatekeeper to a second communication terminal KE2 with the call number 6300. Therefore, a terminal profile P6300 assigned to a second communication terminal KE2 is stored in the second gatekeeper G-B. The third gatekeeper G-C is assigned as home gatekeeper to a third communication terminal KE3 with the call number 6529. Therefore, a terminal profile P6529 assigned to a third communication terminal KE3 is stored in the third gatekeeper G-C.
The address of the first gatekeeper G-A is stored in the first communication terminal KE1 for a connection to the first gatekeeper G-A. In the case of malfunctioning or failure of the first gatekeeper G-A or the network segment N-A, the address of an alternate gatekeeper—in this embodiment of the second gatekeeper G-B—is also stored in the first communication terminal KE1. In order to control the connection setup or a connection to the first communication terminal KE1, a terminal profile P4711 assigned to the first communication terminal KE1 is stored in the second gatekeeper G-B in addition to the terminal profile P6300 of the second communication terminal KE2.
The address of the second gatekeeper G-B is stored in the second communication terminal KE2 for a connection to the second gatekeeper G-B. In the case of malfunctioning or failure of the second gatekeeper G-B or the network segment N-B, the address of the first gatekeeper G-A is also stored as an alternate gatekeeper in the second communication terminal KE2. In order to control the connection setup or a connection to the second communication terminal KE2, a terminal profile P6300 assigned to the second communication terminal KE2 is stored in the first gatekeeper G-A in addition to the terminal profile P4711 of the first communication terminal KE1.
The address of the third gatekeeper G-C is stored in the third communication terminal KE3 for a connection to the third gatekeeper G-C. In the case of malfunctioning or failure of the third gatekeeper G-C or the network segment N-C, the address of the second gatekeeper G-B is also stored as an alternate gatekeeper in the third communication terminal KE3. In order to control the connection setup or a connection to the third communication terminal KE3, a terminal profile P6529 assigned to the third communication terminal KE3 is stored in the second gatekeeper G-B in addition to the terminal profiles P6300 and P4711 of the second and first communication terminal KE2, KE1.
In this way, the terminal profile with call number, authorizations, etc. is duplicated in the home gatekeeper and in the alternate gatekeeper according to the related art for each communication terminal or subscriber. This, considerably burdens the resources, e.g. databases of the gatekeeper of the communication system. In addition, high administrative costs are required for the duplication and, if required, updating the terminal profiles.